1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to golf balls having a core and a cover, with dimples being formed on the cover.
2. Description of the Related Art
Although golf balls having a balata cover prevailed previously, golf balls having a cover composed of a synthetic resin were thereafter developed, which have prevailed at present. Typical synthetic resins are ionomer resins. A variety of grade of ionomer resins have been used for golf balls. An ionomer resin has higher hardness in comparison with balata, and is excellent in a resilience performance. On the other hand, hard feel at impact is experienced according to this golf ball. Hard feel at impact has been avoided by senior golf players, in particular. When a synthetic resin having low hardness (typically, a thermoplastic elastomer) is used, feel at impact of the golf ball is improved. However, a synthetic resin having low hardness results in insufficient resilience performance.
JP-A-113129/2002 discloses a golf ball having a cover composed of a mixture of an ionomer resin and a thermoplastic styrene elastomer. In accordance with this golf ball, both of the resilience performance and the feel at impact are achieved concurrently by using an ionomer resin and a thermoplastic styrene elastomer in combination.
Golf balls having a cover composed of a mixture of an ionomer resin and a thermoplastic styrene elastomer are liable to be back spun compared to golf balls having a cover in which an ionomer resin is used alone. The back spin results in the generation of lift force. Although the lift force is essential in a flight performance of a golf ball, excess lift performance may rather reduce flight distance. Particularly, excess lift force in a high speed area immediately after the impact with a driver results in hopping of the golf ball, and thus the flight distance is drastically reduced. In spite of the excellent resilience performance of the golf ball having a cover composed of the aforementioned mixture, the flight performance is insufficient.